(a) Field of the invention:
The present invention pertains to a transistor amplifier employing a plurality of transistors serving at its amplifying elements, and more particularly it pertains to a multi-stage transistor amplifier of a full stage direct-coupled configuration.
(B) Description of the prior art:
Currently known transistor amplifiers almost invariably adopt the full stage direct-coupled configuration. With such a configuration, it is most important to stabilize the quiescent operating point for each amplifying transistor in the respective stage circuits, particularly in the input stage circuit in order to obtain a good over-all operation stability of the amplifier.
To meet the above requirement, most of the conventional transistor amplifiers according to the prior art are so arranged that their input circuit and/or the subsequent stage circuits are comprised of a differential amplifiers, respectively, of which operation is, as well known, hardly affected by fluctuations in the ambient temperature and in the voltages of the operating power supplies, and/or that there are provided circuit means such as for making compensation for those variations of the quiescent operating point for each amplifying transistor in the respective stage circuits which might be caused by the changes in the ambient temperature and in the voltages of the operating power supplies. As such, the prior art transistor amplifiers have tended to be complicated in their structure.